Arctic Cycles – Related to AMO/PDO,
Not CO2

[last update:
2011/05/21]

Arctic Temperature

The following figures compare the annual average temperature
anomaly data for the Arctic for NOAA GHCN (unadjusted) and Hadley CRUTEM3
(adjusted and averaged over 5x5 degree grids) through 2010. All stations or
grids north of 65N with data extending from before 1930 to after 2000 have
been included. (Plotted at www.appinsys.com/GlobalWarming/Climate.aspx)

GHCN – 29 stations

CRUTEM3 – 32 5x5 grids

The following figure compares the above two figures with
GHCN in blue and CRUTEM3 in red. Hadley/CRU adjustments result in reduction
in past warm years in the 1920s-1940s and slightly warmer temperatures in the
mid-2000s.

The following figure shows the GHCN temperature anomaly data
(blue) along with the same data shifted back
69 years and down 0.3 degrees (red).

The following figure shows the CUTEM3 temperature anomaly
data (blue) along with the same data shifted
back 69 years and down 0.6 degrees (red).

This shows the similarity of the cycles and may portend 25
years of cooling before the warming resumes.

Hansen Says It’s Natural

NASA’s James Hansen (Hansen et al 2007 “Climate
simulations for 1880–2003 with GISS modelE” Clim Dyn (2007) 29:661–696 [http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3.pdf])
observed that the climate model was not correctly simulating the 1930s-1940s
warm period in the global average temperature: “It may be fruitless to search for an
external forcing to produce peak warmth around 1940. It is shown below that the
observed maximum is due almost entirely to temporary warmth in the Arctic. Such Arctic
warmth could be a natural oscillation (Johannessen et al. 2004),
possibly unforced. Indeed, there are few forcings that would yield warmth
largely confined to the Arctic. Candidates might be soot blown to the Arctic
from industrial activity at the outset of World War II, or solar forcing of the Arctic Oscillation (Shindell et al. 1999;
Tourpali et al. 2005) that is not captured
by our present model. Perhaps a more likely scenario is an unforced ocean
dynamical fluctuation with heat transport to the Arctic and positive
feedbacks from reduced sea ice.”

So Hansen asserts that the previous warming cycle was
natural (perhaps “solar forcing of the Arctic Oscillation”), but the
current warming cycle is due to CO2. And yet the current “global” warming has
also been “largely
confined to the Arctic”.

The following figure shows the global temperature change
from 1978 to 2006 for the lower troposphere from satellite data [http://climate.uah.edu/25yearbig.jpg].
Most of the warming has been in the Arctic.

The following figure is from the IPCC Fourth Assessment
Report (AR4) Figure 9.6 (2007). It shows the change in temperature (C per
decade) by latitude. The black line shows the observed temperature, the blue
band shows the output of the computer models including only natural factors,
whereas the pink band shows the output of computer models including
anthropogenic CO2. Notice that the models without CO2 (blue shaded area)
can explain all of the warming for most of the world up to 30 degrees north
latitude. This figure also shows that the warming is mainly in the
Arctic.

So it is Hansen’s and other alarmists’ position that these
two nearly identical Arctic warming cycles have two completely different
causes – 1930s = natural; 1990s = CO2.

It is only in recent years that scientists are starting to
recognize the influence of oceanic cycles in influencing climate. A 2008
study – “Oceanic Influences on Recent Continental Warming”, by Compo et al in
Climate Dynamics, 2008) [http://www.cdc.noaa.gov/people/gilbert.p.compo/CompoSardeshmukh2007a.pdf]
states: “Evidence is
presented that the recent worldwide land warming has occurred largely in
response to a worldwide warming of the oceans rather than as a direct
response to increasing greenhouse gases (GHGs) over land. Atmospheric model
simulations of the last half-century with prescribed observed ocean
temperature changes, but without prescribed GHG changes, account for most of
the land warming. … Several recent studies suggest that the observed SST
variability may be misrepresented in the coupled models used in preparing the
IPCC's Fourth Assessment Report, with substantial errors on interannual and
decadal scales. There is a hint of an underestimation of simulated
decadal SST variability even in the published IPCC Report.”

The Atlantic Multi-Decadal Oscillation (AMO) is a
fluctuation in de-trended sea surface temperatures in the North Atlantic
Ocean. It was identified in 2000 and the AMO index was defined in 2001 as the
10-year running mean of the de-trended Atlantic SST anomalies north of the
equator.

The NatGeo creates alarm about
recent Arctic warming, but ignores the long term data showing that this is a
repeated cycle.

They also make the false claim
“the bays of Greenland’s
southwest coast, where warming temperatures have reduced permanent sea ice.”
– southwest Greenland never had permanent sea ice as shown below. The magenta
line shows the median area of sea ice.